A Quenching and Tempering Treatment Method for Large 34crnimo6 Forgings

Abstract

The invention discloses a hardening and tempering method of a large 34CrNiMo6 forged piece. The method is used for processing the large forged piece with the thickness being larger than or equal to 600 mm and the length being larger than or equal to 10,000 mm. The method includes the following steps of (1), quenching, specifically, the forged piece is subjected to quenching and heating with the quenching temperature being 870-880 DEG C; (2), cooling, specifically, a water-cooling and air-cooling alternative manner is adopted to cool the forged piece, and after final cooling, the surface temperature is controlled to be within 250 DEG C; (3), tempering, specifically, the temperature is raised to 590 + / -5 DEG C, and tempering and heat preservation are performed. By means of the method, the cooling and cracking phenomena of the forged piece in the water cooling process can be effectively prevented, and the optimal cooling speed can be obtained; the process is stable and high in reliability, and the performance of the forged piece meets the assessment requirements; and the phenomenon that quenching oil combustion occurs easily when oil cooling is adopted for the large forged piece can be avoided, and potential safety hazards in production are greatly lowered.

Description

technical field [0001] The invention relates to a heat treatment method, in particular to a quenching and tempering treatment method for 34CrNiMo6 large shaft parts. Background technique [0002] The tie rod material used in the 140MN free forging hydraulic press is 34CrNiMo6, the size of the part is: Φ600×22940mm, and the net weight is 40650kg; the forgings require Rm: 800MPa~980MPa after quenching and tempering, Re≥650MPa, A5≥12%, Aku≥28J. The heat treatment size of the forgings is Φ690×23800mm, and the material forgings are ultra-long and ultra-thick forgings (thickness≥600mm, length≥10000mm). [0003] 34CrNiMo6 is a low-alloy high-strength steel with excellent comprehensive mechanical properties. It is widely used in the manufacture of important parts such as camshafts and connecting rods of engines. It has poor machinability and is generally used in wind power products. [0004] At present, most of the heat treatment methods for 34CrNiMo6 materials focus on the manufac...

AI Technical Summary

Problems solved by technology

However, when it is directly used to process super-long and super-thick large forgings, take the pull rod of the aforementioned hydraulic press as an example, its thickness is too large and its length is too long. The cooling effect is poor and the time is long. In the actual production, it is found that the stability of the forging performance cannot be guaranteed, and the qualification of the forging is low. On the other hand, during the oil cooling process of the shaft with a length of more than 20 meters, it is easy to occur at the contact point of the workpiece, oil and air. Quenching oil combustion phenomenon, there is a great production safety hazard

[0006] Therefore, the above two heat treatment methods of water cooling and oil cooling have obvious defects when they are used for quenching and tempering treatment of super-long and super-thick large forgings.

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